1. Field of the Invention
This invention relates to a waterproof camera with focusing means or an automatic focusing mechanism incorporated therein and more particularly to a camera designed to facilitate lens focusing at a given distance for underwater photography.
2. Description of the Prior Art
A known automatic focusing mechanism which operates on the basis of detected brightness or contrast of an object to be photographed cannot perform distance measurement unless the object brightness is above a certain level. Underwater, where the object is to be photographed, not only has low contrast but also has a low degree of brightness. Distance measurement is difficult for an automatic focusing mechanism of this type. When using an automatic focusing mechanism of another known type performing the distance measurement on the basis of infrared rays reflected from the photographing object, underwater distance measurement cannot be satisfactorily performed because the infrared rays are absorbed by water. It has, thus, been impossible to use an automatic focusing mechanism for underwater photography. Therefore, the conventionally practiced methods for underwater photography have included a manual distance measuring method in which photography is performed by adjusting the focal point of a lens depending on the result of distance measurement performed with the eye; and a fixed focus method in which the focal point of the lens is fixed at a position corresponding to a distance of about three meters and the aperture of the lens is stopped down to obtain a sufficient field depth to obtain a photography range from the nearest distance to an infinite distance. However, the manual distance measuring method necessitates a troublesome focusing operation, although accurate focusing can be performed. Under water, the photographer must repeatedly come up to the surface to breathe. It is not easy for the photographer to estimate the distance and focus the lens. Therefore, it has been difficult to carry out reliable underwater photography using the manual distance measuring method. When using the fixed focus method, on the other hand, although there is not such troublesome operation to focus the lens every time, it is impossible to sharply photograph objects over the total range from the nearest distance to infinite distance, since there is some blurring for objects located near or far. Particularly in underwater photography, the objects to be photographed (fishes, coral) and often located at a distance of only one meter or so. Close-up photography is thus frequently required. When using conventional fixed focus cameras, the nearest photographable distance is generally 1.5 m or thereabouts. It has been almost impossible to take sharp photographs of objects located at closer distances, such as one meter.
It is an object of the present invention to provide a waterproof camera permitting underwater photography, wherein there are provided focusing means for adjusting the focal point of a photo-taking lens and operation means for adjusting the focal point of the lens to a position suited for underwater photography. For ordinary photography (land photography), the above focusing means permits accurately focused photography; and, for underwater photography, the above operation means adjusts the photo-taking lens to a focus position suited for underwater photography, so that the operability and performance of the camera can be enhanced for underwater photography.
It is a second object of the invention to provide a camera of the above kind, wherein the focusing means is composed of an automatic focusing mechanism improving operability and performance in ordinary photography.
It is a third object of the invention to provide a camera of the above kind, wherein the operation means automatically operates in response to an underwater photographic operation.
These and further objects of the invention will become apparent from the following detailed description of preferred embodiments thereof taken in conjunction with the accompanying drawings.